Various types of armor are known in the art. The majority of armor produced to date are made of steel, but ceramic armor is also known.
Typically, steel armor is heavier than ceramic armor. Steel armor has a number of significant disadvantages. In the case of body or vehicle armor, higher weight reduces mobility. Heavier armor also tends to be bulkier and less flexible, which is a problem in particular with armored vests.
Also known is armor that employs light-weight materials such as fabrics comprised of aramid fibers, ultra-high molecular weight polyethylene fibers, carbon fibers and liquid crystal polyester fibers, as well as high density, light-weight, hard materials, such as titanium, alumina oxide ceramic, boron carbide ceramic, silicon carbide ceramic, glass ceramic and metal-matrix ceramics, and ultra hard metals. To achieve maximum efficiency, these materials are frequently stacked upon one another to progressively destroy the penetrator. One of the most successful multi-layer types of materials for use against high-energy impacts, such as those caused by high-velocity rifle bullets, employs a strike-face comprising the hardest available material such as light-weight ceramics. The strike-face layer is applied (e.g. by lamination or gluing) upon a stiff energy absorbing material which may be material such as the fabrics mentioned above, or combinations thereof. The most commonly employed material is boron carbide ceramic tiles arranged side by side, in a multiple tile configuration with mating edges affixed to an ultra-high molecular weight polyethylene (UHMWPE) laminate. The thickness and density of both the ceramic and laminate are engineered to be sufficient to defeat the specified threat.
Functionally, when the strike-face of a ceramic tile is impacted, it destroys the penetrative ability of the impactor by radical deformation and, should the impactor have sufficient remaining energy to pass beyond the ceramic tile, the minor remaining energy is absorbed by an underlying laminate. The intimate adhesion of the ceramic to the laminate is of primary importance since unsupported ceramic is by nature brittle and requires a rigid backing support. The absence of such a support would cause the resistance to decrease significantly, leading to failure to meet the desired level of impact-resistance. Another requirement of such a construction is for the mating edges to be placed tightly against one another, in case the impactor strikes the joint of two or more tiles.
Today, ceramic armor is generally of two basic geometries: single large monolithic tiles or smaller tiles arranged in a manner that minimizes gaps between the tiles. In all cases, the ceramic is expected to be penetrated, therefore an energy-absorbing component is integrated behind the ceramic to capture and dissipate the remaining energy of the penetrator and any remnants of the penetrator.
Recent laboratory testing has revealed several interesting mechanical penetration phenomena associated with ceramics under containment by a more ductile material such as steel. Containment in these experiments entails the total encapsulation of a ceramic armor element (usually a tile) by a metal of known impact resistance in a welded construction firmly mounted on a structure of sufficient strength to tolerate the impact of a heavy impactor (usually a long pointed metallic rod) (INTERFACE DEFEAT and PENETRATION: TWO MODES OF INTERATION BETWEEN METALLIC PROJECTILES and CERAMIC TARGETS; LUNDBERG, P.; UNIVERSITY of UPPSALA; 2004.)
Contained ceramic has significantly increased impact resistance than the same ceramic uncontained. In actual practice and application in the field, containment of ceramics in such a manner is impractical except in the largest vehicles or structures.
The measure of the impact resistance is usually characterized by the energy required to penetrate or destroy the material being impacted. In the case of ceramic armor elements, the projectiles typically are lower in hardness than the ceramic element, but with a much higher resistance to brittle fracture. In the field of ceramic armors, it is well known that the ceramic is progressively destroyed by a process known as ‘interface defeat’ (A DETAILED COMPUTATIONAL ANALYSIS OF INTERFACE DEFEAT, DWELL AND PENETRATION FOR A VARIETY OF CERAMIC TARGETS; T. J. HOLQUIST and G. R. JOHNSON; U.S. ARMY HIGH PERFORMANCE COMPUTING RESEARCH CENTER. September 2002).
Contained ceramic tiles tested in this manner typically exhibit a resistance to penetration approximately 1.3 to 1.8 times that of an uncontained tile (AMPTIAC QUARTERLY VOL. 8 NUMBER 4 2004 ARMY MATERIALS RESEARCH, http://ammtiac.alionscience.com).
Ceramic structures in protection armor typically use have parallel flat surfaces. Recently however, ceramic pellets encapsulated in a metallic or plastic matrix material have been used (EP 1 363 101, U.S. Pat. No. 6,575,075, US 2006/0243127, US 2004/0083880). These systems typically exhibit increased thickness, weight and processing requirements, compared to conventional parallel-surfaced ceramic armor systems.
U.S. Pat. No. 5,221,807 discloses protection armor comprising an armor plate for stopping projectiles with an auxiliary plate disposed in front thereof, the auxiliary plate being constituted by a ceramic plate pierced by a large number of blind holes distributed in a regular mesh extending perpendicularly from the impact side towards the rear side. The effect of the auxiliary plate is to destabilize and to score the projectiles so as to enhance their tendency to shatter on striking the armor plate. The auxiliary plates disclosed in U.S. Pat. No. 5,221,807 are distinguished from armor plates of the present invention in that the multiple depressions of the auxiliary plate are not filled with a second material, and are not sealed by a rigid layer of a third material.
U.S. Pat. No. 4,665,794 discloses an armor plate comprising multiple depressions, which are filled with a plurality of packing bodies in an irregular or regular fashion. The packing bodies are hollow-bodied and consist of a non-metallic material such as glass or ceramic. The interspaces between the packing bodies are filled out with plastic material, preferably polyurethane foam. The armor plate of U.S. Pat. No. 4,665,794 is distinguished from armor plates of the present invention, in that the plates of U.S. Pat. No. 4,665,794 are metal plates, and no rigid layer of a third material is provided.
U.S. Pat. No. 6,575,075 discloses a composite armor construction for absorbing and dissipating kinetic energy from high velocity projectiles. The construction includes an internal layer of pellets, which are bound and retained by a solidified material. The pellets may contain holes which can optionally be filled with a solidified material. The present invention is distinguished from the construction of U.S. Pat. No. 6,575,075 in that the ceramic material disclosed therein is in form of pellets, and not in form of a rigid monolithic tile. No rigid layer of a third material, fixedly attached to the ceramic plate is disclosed.
GB 2147977 discloses a ceramic tile with a filleted area at its edges designed to strengthen the edges of the tile. The resulting depression is optionally filled with a second material, such as epoxy, polyester or acrylic resin. GB 2147977, however, does not disclose a rigid layer of a third material, sealing the second material between the ceramic tile and the rigid layer.
WO 99/11997 discloses an armor according to the preamble of claim 1. This document, however, does not disclose the characterizing part of the claim, i.e. it does not disclose at least one depression at a side opposite the strike-face of the armor.